This invention relates generally to medical devices used during vascular intervention, and more particularly, concerns medical devices that are useful in treating thromboembolic disorders and for removal of foreign bodies in the vascular system.
Thromboembolic disorders, such as stroke, pulmonary embolism, peripheral thrombosis, atherosclerosis, and the like, affect many people. These disorders are a major cause of morbidity and mortality in the United States and throughout the world. Thromboembolic events are characterized by an occlusion of a blood vessel. The occlusion is caused by a clot which is viscoelastic (jelly-like) and is comprised of platelets, fibrinogen, and other clotting proteins.
When an artery is occluded by a clot, tissue ischemia (lack of oxygen and nutrients) develops. The ischemia will progress to tissue infarction (cell death) if the occlusion persists. Infarction does not develop or is greatly limited if the flow of blood is reestablished rapidly. Failure to reestablish blood-flow can lead to the loss of limb, angina pectoris, myocardial infarction, stroke, or even death.
Occlusion of the venous circulation by thrombi leads to blood stasis which can cause numerous problems. The majority of pulmonary embolisms are caused by emboli that originate in the peripheral venous system. Reestablishing blood flow and removal of the thrombus is highly desirable.
There are many existing techniques employed to reestablish blood flow in an occluded vessel. One common surgical technique, an embolectomy, involves incising a blood vessel and introducing a balloon-tipped device (such as the Fogarty catheter) to the location of the occlusion. The balloon is then inflated at a point beyond the clot and used to translate the obstructing material back to the point of incision. The obstructing material is then removed by the surgeon. While such surgical techniques have been useful, exposing a patient to such surgery may be traumatic and is best avoided when possible. Additionally, the use of a Fogarty catheter may be problematic due to the possible risk of damaging the interior lining of the vessel as the catheter is being withdrawn. Further, the balloon of the Fogarty catheter may not successfully retain all of the obstruction when pulled through the tortuous vasculature.
Percutaneous methods are also utilized for reestablishing blood flow. A common percutaneous technique is referred to as balloon angioplasty where a balloon-tipped catheter is introduced into a blood vessel, typically through an introducing catheter. The balloon-tipped catheter is then advanced to the point of the occlusion and inflated in order to dilate the stenosis. Balloon angioplasty is appropriate for treating vessel stenosis but is generally not effective for treating acute thromboembolisms.
Another percutaneous technique is to place a microcatheter near the clot and infuse Streptokinase, Urokinase, or other thrombolytic agents to dissolve the clot. Unfortunately, thrombolysis typically takes hours to days to be successful. Additionally, thrombolytic agents can cause hemorrhage and in many patients the agents cannot be used at all.
Another problematic area is the removal of foreign bodies. Foreign bodies introduced into the circulation can be fragments of catheters, pace-maker electrodes, guide wires, and erroneously placed embolic material such as thrombogenic coils. There exist retrieval devices for the removal of foreign bodies, certain of such devices forming a loop that can ensnare the foreign material by decreasing the size of the diameter of the loop around the foreign body. The use of some such removal devices can be difficult and sometimes unsuccessful. For example, some of these devices may fail to completely capture the obstruction.
Various thrombectomy and foreign matter removal devices have been disclosed in the art. However, such devices have been found to have structures that are either highly complex or lacking in sufficient retaining structure. Disadvantages associated with the devices having highly complex structure include difficulty in manufacturability as well as use in conjunction with microcatheters. Other less complex devices tend to pull through clots, due in part to the lack of experience in using the same, or are otherwise inadequate in capturing clots or foreign bodies. Additionally, many of the prior art thrombectomy devices carry with them a significant risk of producing distal embolization as a thrombus is disrupted. It would be desirable to provide for the quick removal of a thrombus while still intact, thus restoring native blood flow and minimizing the production of emboli.
Moreover, systems heretofore disclosed in the art are generally limited by size compatibility and the increase in vessel size as the emboli is drawn out from the distal vascular occlusion location to a more proximal location near the heart. If the embolectomy device is too large for the vessel it will not deploy correctly to capture the clot or foreign body, and if too small in diameter it cannot capture clots or foreign bodies across the entire cross section of the blood vessel. Additionally, if the embolectomy device is too small in retaining volume then as the device is retracted the excess material being removed can spill out and be carried by flow back to occlude another distal vessel. These and other problems are solved by the present invention.
What has been needed and heretofore unavailable is an extraction device that can be easily and controllably deployed into the circulatory system for the safe and effective removal of clots and foreign bodies. Moreover, due to difficult-to-access anatomy such as the cerebral vasculature and the neurovasculature the invention should possess a small collapsed profile and preferably be self-expanding to allow the device to be delivered through the lumen of commercially available catheters. It is also important that the system minimize occlusion of the vessel. Notably, the invention should provide an improved level of ability to safely capture clots and foreign material in the blood. The present invention satisfies these needs.